The thing with young children is... their scratches heal very quickly and it does not scar.
But remember, that scabs and the following so called "scar" can take time to go away.
The epidermis replaces skin cells, regularly. But it is a process.
The scratch your son has, is not a deep.... scratch.
Its just a cut.
Neosporin itself is not going to stop it from scarring. Neosporin is used to prevent infection. But your son's cut... already scabbed over. It is not a raw bleeding cut, anymore.
Your son's cut... IS already healing. It has a scab. Let is process.
Even after the scab falls off... there will MIGHT be an indication that a cut was there... because, sometimes you have a slight line of demarcation, of where a cut used to be. BUT, this often goes away. In time.
Put sunscreen over the healed cut, if there is scar tissue.
But I doubt your son's cut will form heavy tissue scarring on it... because, it was just a superficial cut.
My kids, have had many cuts/scrapes... everywhere on their body, and they don't have, a scar. Scars, are not always permanent. It depends on the type of wound.... and the type of skin a person has, as well.